This project seeks to develop an earphone for diagnostic audiometry with features that will significantly increase the efficiency and decrease the cost of routine hearing testing. The most-often used earphones employ a supra-aural design that has several undesirable characteristics, including 1) an "occlusion effect", an artificial increase in sensitivity to bone-conducted stimuli; 2) poor ambient noise exclusion; 3) high inter-subject variability in sound pressures delivered to human ears; and 4) poor comfort. The occlusion effect necessitates that the test ear be uncovered during bone conduction testing. This requires that the tester change the transducer arrangement several times during pure tone testing. In manual testing, this requirement can add several minutes to the test time. For automated testing, the need to reposition transducers several times during the test is counterproductive to the goal of reducing tester intervention. The poor ambient noise exclusion requires that testing be performed in expensive sound rooms. The inter-subject variability increases the variance associated with threshold measures. The poor comfort limits the time that some patients will participate in the test. Other earphones are available that address some, but not all, of these problems. In this project, an earphone will be developed that 1) minimizes the occlusion effect permitting pure tone and speech hearing tests to be conducted with a single transducer arrangement and facilitating automated test methods; 2) increases ambient noise exclusion, eliminating (in many environments) the need for sound-attenuating rooms; 3) decreases inter-subject variability; and 4) increases comfort. In addition to meeting these goals, the earphone must have a frequency response that is similar to other audiometric earphones to avoid significant changes in the frequency content of stimuli used for speech tests. During the Phase I project several prototypes have been developed and evaluated. The preliminary data obtained in Phase I indicates that the current design has a significantly reduced occlusion effect, good ambient noise exclusion, a more stable coupling to the ear for reduced inter-subject variability, excellent comfort, and an excellent frequency response. Although this design is adequate to meet the requirements for automated testing and increased efficiency of manual testing, additional improvements will be explored in Phase II. These will include elimination of the residual occlusion effect at 250 Hz and increased output. These can be accomplished by modification of the enclosure and replacing the transducer with a more efficient device. /Relevance Millions of hearing tests are conducted each year in the US with methods that are essentially unchanged in the last five decades. The tests are usually conducted by highly trained professionals in expensive sound-treated rooms. This project is a component of a research and development program to develop efficient, accurate, automated hearing tests. Automated testing cannot be performed with the earphones most commonly used for hearing testing. In this project an earphone is being developed that can be used in both automated and manual testing and will significantly increase the efficiency, accuracy, and accessibility. [unreadable] [unreadable] [unreadable]